1. Field of the Invention
This invention relates in general to a vehicle outer panel structure and a method of producing the same, and more particularly to such a method of producing the vehicle outer panel structure which is excellent in heat-insulation characteristics and reinforcement characteristics for a vehicle outer panel.
2. Description of the Prior Art
Recently, a vehicle outer panel has been eagerly desired to obtain comfort in a vehicle passenger compartment upon improving heat-insulation and to obtain high rigidity upon being reinforced.
First, the meaning of heat-insulation will be discussed. Generally considerable heat flows into the vehicle passenger compartment and flows out to the outside of the passenger compartment through doors, fenders, floor, roof, dash board panel and the like. As a result, in order to suppress the inflow or outflow of the heat, a variety of heat-insulation material such as felt or glass mat is attached to the back side of a vehicle outer panel. For example, a roof panel tends to receive sun light and therefore is subjected to a high temperature of 80.degree. to 100.degree. F. in summer, so that much heat flows into the vehicle compartment through the roof panel. For the purpose of preventing this heat inflow, a heat-insulation structure such as shown in FIGS. 2 and 3 has been employed. The heat-insulation structure in FIGS. 2 and 3 includes a vehicle outer panel structure having a heat-insulation material 6 adhered to an adhesive double coated tape 5 which is adhered to the back side of a vehicle outer panel 1. In this example, listing wires 3 are extended below the vehicle outer panel structure. Additionally, a head lining 4 is supported in a pending manner by the listing wires 3. The heat-insulation material 6 is formed of felt of natural or synthetic fiber or glass mat. In addition, a similar heat-insulation material is attached to the back side of a floor panel, a dash board panel and the like. Thus, heat-insulation of the vehicle passenger compartment is accomplished by means of heat-insulation materials discussed above.
Next, necessity of high rigidity of the vehicle outer panel will be discussed hereinafter. Weight-lightening of automotive vehicles has been promoted from the viewpoints of saving resources and energy. This weight-lightening is accomplished by reducing the thickness of a vehicle outer panel or decreasing the number of structural members. However, this unavoidably lowers the strength of various component parts and causes shortage of surface extension rigidity of outer panel, thereby deteriorating rigidity feeling, particularly in the case of an automotive vehicle door. In order to solve these problems, it has been proposed to use a reinforcement material for reinforcing a vehicle door panel as disclosed in Japanese Utility Model Provisional Publication No. 55-101659. Such a structure is shown in FIG. 4 in which a reinforcement material 8 formed of thermosetting plastic is attached to the back side of a door panel 7.
However, the following difficulties have encountered in the above-discussed heat-insulation material and the reinforcement material. First, heat-insulation material is previously fabricated in a desired shape and is attached to the outer panel, in which the heat-insulation material is generally large-sized and therefore is troublesome to attach. Second, the reinforcement material is a fabricated member formed of the thermosetting plastic containing glass fiber and cross-shaped. However, this reinforcement material is insufficient in heat-insulation.